def isPalindrome(self, s: str) -> bool:
    left, right = 0, len(s) - 1
    while left < right:
        while left < right and not s[left].isalnum():
            left += 1
        while left < right and not s[right].isalnum():
            right -= 1
        if left < right:
            if s[left].lower() != s[right].lower():
                return False
            left, right = left + 1, right - 1
    return True
